A native of Frederick, Maryland, Shawn Hatosy was a singer in his own band and graduated from Linganore High School in 1994. He starting acting at the age of 10 for a local theatre, and his first television appearance was on episode of Homicide: Life on the Streets.
After moving to New York in 1995, Shawn was featured in an episode of Law and Order. He began his film career in 1996 with movies such as No Way Home and All Over Me. In 1998, he starred in The Faculty. He then had a starring role in Outside Providence in 1999. In 2000, he appeared in the teen drama Down to You, followed by Borstal Boy.
Shawn has guest-starred in numerous television programs, but his most notable role is Det. Sammy Bryant on Southland.